It is widely assumed that the architecture of trabecular bone is related through "Wolff's Law" to functionally imposed stresses, but quantitative formulations of this law do not exist. The objective of this research is to provide correlations between trabecular morphological parameters determined from quantitative automated stereology and global stress distributions predicted from finite element analysis. Making use of a three-part patellar tendon, the equine patella is used as a model to study in-vivo alterations in stress distributions by: a) transection of medial or central patellar tendons; and b) implantation of smooth and porous high modulus spherical inclusions. Resulting global changes in trabecular architecture are monitored in three-dimensions using a new computerized video stereology system. Three-dimensional finite element models are generated using ADINA, interfaced with pre- and post- processing software packages, FEMGEN and FEMVIEW. Input data for the models are generated from direct measurements of patellar geometry and trabecular modulus and from in-vitro measurements of patello-femoral contact areas. In-vivo strain gage and buckle transducers studies are used to determine in-vivo loading patterns and subsequently to provide in-vitro validation of the finite element models. The finite element predictions are compared with stereologic data to explore our working hypotheses that trabecular bone is formed in regions of high shear stress and is aligned so as to minimize bending in individual trabeculae.